Bob - The formulas for area are constant, whether you're plugging in inches or mm or cubits.

Area of a circle = pi r(squared)
Area of an ellipse (oval) = pi r1 r2

So for a standard 40mm x 30mm cab
the area would be ~3.1416 x 20mm x 15mm = 942.48 square mm.

You're example asks about perimeter measurements, not area. Different can of worms.
Length of wire wrapped around 16mm diameter dowel = pi d = ~3.1416 x 16mm = 50.27mm.
The perimeter of an ellipse is a lot more complicated, involving calculus. I would just cut a 50mm piece of wire, shape it to your choice of oval (20, 30, 40 degree, whatever) and measure that.

From Rich T. - October 05, 2009 at 11:00:15

Message: 68392